Angiographic classification of the inferior sagittal sinus based on the venous drainage patterns

The inferior sagittal sinus (ISS) and its tributaries have received little attention because of its inconspicuous appearance, and its anatomical variations are also unknown. This study aimed to evaluate the morphological variations of the ISS.

We retrospectively reviewed 518 patients in whom cerebral angiography was clinically indicated. The detailed angioarchitecture of the cerebral venous system, including the ISS and their tributaries, and the morphological variations of the ISS were evaluated. Abnormalities of the rostral third superior sagittal sinus (SSS) were also evaluated.

The ISS was visualized in 270 (52.1%) patients. We proposed an angiographic ISS classification according to the venous drainage patterns: Type 0, not visualized; Type 1, small ISS with faint tributaries; Type 2, moderate ISS with developed tributaries; and Type 3: large ISS with well-developed tributaries, which are responsible for the venous drainage of the anterior frontal lobe. The frequency of each ISS type was as follows: Type 0, 248 (47.9%); Type 1, 211 (40.7%); Type 2, 44 (8.5%); and Type 3, 15 (2.9%). The mean ISS size was significantly larger with an increase in the type of ISS (p < 0.0001). The rostral third SSS hypoplasia was observed in all cases of Type 3. The hypoplasia of the rostral third SSS and development of the ISS were strongly correlated and complementary to each other.

This study provided the angiographic ISS classification, and our proposed angiographic ISS classification could be helpful in better understanding of the ISS anatomy and its venous drainage pattern.